1. Field of Invention
This invention relates generally to a sheet feeder for an image forming engine of an image forming apparatus.
2. Description of Related Art
To supply image recording media, generally referred to as "sheets", to the image forming engine, individual copy sheets are acquired from the top of a stack and are transported forward by a translating vacuum feed head into a set of take away nip rolls. Sheet fluffers separate a sheet from the top of the stack and the translating vacuum feed head acquires the separated sheet and feeds the separated sheet into the set of take away nip rolls. The time for the translating vacuum feed head to acquire the sheet is relatively short. If the fluffing or vacuum pressures increase, the sheet acquisition time decreases. Accordingly, the risk of more than one sheet being moved into the take away nip rolls (i.e., a multifeed error) also increases. If fluffing pressure decreases, the top sheet may not get close enough to the translating vacuum feed head which may result in no sheet being fed (i.e., a misfeed error) or in late acquisition of the sheet when the translating vacuum feed head moves forward toward the take away nip rolls. The fluffer and vacuum pressures are determined by paper characteristics, such as the sheet basis weight measured in grams per square meter (gsm), size and coating, which are input by the user or determined automatically by sensors in the image forming apparatus.